I'm writing a--well, you probably already have the general idea.
Anyway, let us say, for the purposes of a story, that an adult horse (think thoroughbred or Arabian mare, if the exact size or conformation matters, say around fifteen hands and about 800 pounds, a young adult in very good overall health) is subjected to complex and invasive emergency abdominal surgery in order to save her life. (let's say that her owners regarded her as a beloved pet, or a tremendously expensive investment in a brood mare from a champion bloodline, and didn't want her put down, and someone guessed, correctly, that she could be saved, if you're wondering why she wouldn't just have been euthanized there and then).
How long would it likely take the mare to recover? How long before she regained consciousness after the surgery, how long before she could walk or run? What complications are likely? What would her care involve, in the hours and days after the surgery? Would she be on any kind of medication after the surgery, and if so, what types are likely or at least plausible, and for how long?